In error-prone transmission environments (e.g., the Internet, wireless networks, and so forth), a transmitted video bitstream may suffer corruptions caused by channel impairment. A common situation encountered in some practical systems is that certain compressed video frames are dropped from a bitstream. It is especially true for low bit-rate applications where a frame is small enough to be coded into a transmit unit, such as a real time transport protocol (RTP) packet. At the receiver end, a robust video decoder should be able to handle the frame losses.
Moreover, when a frame is lost in a corrupted bitstream, frame-based error concealment methods can be used to conceal the lost frame. One prior art approach to frame-based error concealment requires that a reference frame that is received and decoded before a detected lost frame be used as the reference frame for the lost frame. According to the prior art approach, the existence of the previously received and decoded reference frame is always assumed. However, this practice does not necessarily produce the best concealment performance for some specific frames or bitstream patterns and, thus, may result in unnecessary degradation of concealment quality.